| Summary: | The immune response implicated in Coronavirus disease 2019 (COVID-19) pathogenesis remains to be fully understood. The present study aimed to clarify the alterations in CD4<sup>+</sup> and CD8<sup>+</sup> memory T cells’ compartments in SARS-CoV-2-infected patients, with an emphasis on various comorbidities affecting COVID-19 patients. Peripheral blood samples were collected from 35 COVID-19 patients, 16 recovered individuals, and 25 healthy controls, and analyzed using flow cytometry. Significant alterations were detected in the percentage of CD8<sup>+</sup> T cells and effector memory-expressing CD45RA CD8<sup>+</sup> T cells (TEMRA) in COVID-19 patients compared to healthy controls. Interestingly, altered percentages of CD4<sup>+</sup> T cells, CD8<sup>+</sup> T cells, T effector (TEff), T naïve cells (TNs), T central memory (TCM), T effector memory (TEM), T stem cell memory (TSCM), and TEMRA T cells were significantly associated with the disease severity. Male patients had more CD8<sup>+</sup> TSCMs and CD4<sup>+</sup> TNs cells, while female patients had a significantly higher percentage of effector CD8<sup>+</sup>CD45RA<sup>+</sup> T cells. Moreover, altered percentages of CD8<sup>+</sup> TNs and memory CD8<sup>+</sup>CD45RO<sup>+</sup> T cells were detected in diabetic and non-diabetic COVID-19 patients, respectively. In summary, this study identified alterations in memory T cells among COVID-19 patients, revealing a sex bias in the percentage of memory T cells. Moreover, COVID-19 severity and comorbidities have been linked to specific subsets of T memory cells which could be used as therapeutic, diagnostic, and protective targets for severe COVID-19.
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